26 



Ranch), upper Big Sheep Creek, Horse Prairie Creek (see 

 below), and Grasshopper Creek (near the townsite of 

 Bannack) . 



3. Occurrences in the study area: One population was found in 

 the "Rocky Hills" (004) between Grant and Bannack. An 

 Element Occurrence Record and map showing the precise 

 location of the occurrence are included in Appendix C. 



D. Habitat 



1. Associated vegetation: In the Rocky Hills, chicken sage 

 grows in openings in a limber pine (Pinus flexilis) and 

 mountain mahogany (Cercocarpus ledifolius) community. 

 Subdominant grasses in this habitat include Elymus spicatus 

 and Koeleria macrantha. Associated forbs include Erigeron 

 compositus , Erigeron tweedy i, Haplopappus acaulis, Ivesia 

 gordonii, Penstemon aridus, and Penstemon eriantherus; all 

 of these plants are characteristic of limestone outcrops. 

 The site was in near pristine condition. A photographic 

 slide showing the habitat is attached at the end of this 

 report. The vegetation at the site near Bannack is very 

 similar, and at the site near Dell, at least two of the forb 

 associates are the same. At the occurrence in the drainage 

 of upper Big Sheep Creek, however, the habitat is an unusual 

 alkaline bottomland community dominated by low sagebrush 

 (Artemisia arbuscula) and greasewood (Sarcobatus 

 vermiculatus ) . 



2. Topography: Four of the sites in Montana are in upland 

 positions on slopes and ridges in the foothills, the fifth 

 is in a basin. The elevations range from about 5,900 to 

 6,900 feet. In the Rocky Hills, Sphaeromeria argentea grows 

 in mid-slope positions on rocky, southwest facing slopes at 

 6,400 to 6,800 feet. 



3. Soil relations: Soils at the Rocky Hills site are shallow 

 gravelly clays derived from limestone. Chicken sage also 

 grows here in cracks in the limestone pavement. The soil at 

 the Bannack site is similar, and the soil at the upper Big 

 Sheep Creek site is also a calcareous clay, while that near 

 Dell was cited as a gravelly clay. 



E. Population demography and biology 



1. Demographic details: Estimates of population size in 



Beaverhead County range from about 100 plants at upper Big 

 Sheep Creek, to thousands of plants observed in 1994 at each 

 of the Rocky Hills and Bannack sites. The Rocky Hills 

 occurrence was estimated to consist of between 5,000 and 

 10,000 plants covering 50 acres in 3 subpopulations . 



